The invention relates, in general, to ceramic body presses and, more particularly, to an improved flywheel and screw press for producing ceramic or refractory articles.
In the pressing of ceramic or similar parts, where the original material is a ceramic powder of a blend of silicates with binders, it is known that two phases are needed. A first phase is needed for the elimination or air and a second phase is needed for the compression. The first phase elimination of air step is the more delicate because it is related to the material plasticity characateristics, with regulation of the intensity of the pressing and of the increase and reduction curve. The compacting pressure has to be constant for all parts, and the pressure for the elimination of air varies from 1/30 to 1/4 of the compacting pressure.
Research demonstrates that the interval between the first pressing step for the elimination of air and the final pressing step may be very short, shorter than the ones permitted by the present mechanical means. The power needed for a perfect elimination of the air could also be reduced with a better control of the first phase for the elimination of air.
U.S. Pat. No. 3,359,608, issued to the present inventor, discloses a friction and screw press for the manufacture of ceramic articles. The press of the present invention is an improvement of the press disclosed in U.S. Pat. No. 3,359,608 which is hereby incorporated by reference.
With the press construction of U.S. Pat. No. 3,359,608, a first and second compacting step were performed by a screw spindle, so that much of the pressing cycle time was consumed by the displacement of the screw spindle. Indeed, in the first compacting step, the flywheel had to be thrown at high speed to reduce the time of its vertical stroke and also, immediately braked before the impact to reduce its pressure. In this step, consequently, a great portion of the kinetic powerimpressed on the flywheel was lost. The second compacting step was performed by imparting an inverted rotation of about one-quarter turn to the flywheel and which was inverted to perform the second and strong compacting step immediately after.
As the flywheel had to acquire a great kinetic power in the rotation of one-quarter turn, a large horsepower motor was necessary and the friction means were consumed in a short working time. Moreover, the sum of the times inherent to the first and second pressing step impeded reduction of the period of a complete compacting cycle; and, the period was always greater than three seconds.